junction/src/Junction.App/Views/MachineConfigView.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:vm="clr-namespace:Junction.App.ViewModels"
             mc:Ignorable="d"
             x:Class="Junction.App.Views.MachineConfigView"
             x:DataType="vm:MachineConfigViewModel"
             x:CompileBindings="True">

  <DockPanel Margin="20">

    <!-- Header -->
    <TextBlock DockPanel.Dock="Top" Classes="h1"
               Text="{Binding Title}"
               Margin="0,0,0,16" />

    <!-- Action bar -->
    <StackPanel DockPanel.Dock="Bottom" Orientation="Horizontal" Spacing="12" Margin="0,16,0,0">
      <Button Classes="accent" Content="Save" Command="{Binding SaveCommand}" IsDefault="True" />
      <Button Content="Cancel" Command="{Binding CancelCommand}" />
    </StackPanel>

    <!-- Inline validation hint -->
    <TextBlock DockPanel.Dock="Bottom"
               Text="{Binding ValidationError}"
               IsVisible="{Binding HasValidationError}"
               Foreground="{DynamicResource DangerBrush}"
               TextWrapping="Wrap"
               Margin="0,12,0,0" />

    <!-- Form -->
    <Border DockPanel.Dock="Top" Classes="card" MaxWidth="480" HorizontalAlignment="Left">
      <StackPanel Spacing="12">

        <StackPanel Spacing="4">
          <TextBlock Classes="fieldLabel" Text="Name" />
          <TextBox Text="{Binding Name}" Watermark="Machine name" />
        </StackPanel>

        <StackPanel Spacing="4">
          <TextBlock Classes="fieldLabel" Text="Protocol" />
          <ComboBox ItemsSource="{Binding AvailableProtocols}"
                    SelectedItem="{Binding SelectedProtocol}"
                    HorizontalAlignment="Stretch"
                    PlaceholderText="Select a protocol" />
        </StackPanel>

        <StackPanel Spacing="4">
          <TextBlock Classes="fieldLabel" Text="Agent URL" />
          <TextBox Text="{Binding AgentUrl}" Watermark="http://host:5000" />
        </StackPanel>

        <StackPanel Spacing="4">
          <TextBlock Classes="fieldLabel" Text="Poll Interval (seconds)" />
          <TextBox Text="{Binding PollIntervalSeconds}" Width="120" HorizontalAlignment="Left" />
        </StackPanel>

      </StackPanel>
    </Border>

    <!-- Data items to monitor (fills remaining space) -->
    <Border Classes="card" Margin="0,16,0,0" MaxWidth="640" HorizontalAlignment="Left">
      <DockPanel>

        <TextBlock DockPanel.Dock="Top" Classes="h2" Text="Data items to monitor"
                   Margin="0,0,0,8" />

        <!-- Controls row -->
        <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Spacing="8" Margin="0,0,0,8">
          <Button Content="Load available items"
                  Command="{Binding LoadItemsCommand}" />
          <Button Content="Select all"
                  Command="{Binding SelectAllCommand}" />
          <Button Content="Select none"
                  Command="{Binding SelectNoneCommand}" />
          <ProgressBar IsIndeterminate="True"
                       IsVisible="{Binding IsProbing}"
                       Width="120" VerticalAlignment="Center" />
        </StackPanel>

        <!-- Status message -->
        <TextBlock DockPanel.Dock="Top" Classes="subtle"
                   Text="{Binding ItemsStatus}"
                   IsVisible="{Binding HasItemsStatus}"
                   TextWrapping="Wrap" Margin="0,0,0,8" />

        <!-- Column header -->
        <Border DockPanel.Dock="Top"
                BorderThickness="0,0,0,1"
                BorderBrush="{DynamicResource CardBorderBrush}"
                Padding="0,0,0,4" Margin="0,0,0,4">
          <Grid ColumnDefinitions="Auto,2*,1.2*,1.2*,1*" Margin="0,0,8,0">
            <TextBlock Grid.Column="0" Text="" Width="28" />
            <TextBlock Grid.Column="1" Classes="fieldLabel" Text="Name" />
            <TextBlock Grid.Column="2" Classes="fieldLabel" Text="Type" />
            <TextBlock Grid.Column="3" Classes="fieldLabel" Text="Category" />
            <TextBlock Grid.Column="4" Classes="fieldLabel" Text="Units" />
          </Grid>
        </Border>

        <!-- Scrollable checklist -->
        <ScrollViewer MaxHeight="320">
          <ItemsControl ItemsSource="{Binding AvailableItems}">
            <ItemsControl.ItemTemplate>
              <DataTemplate x:DataType="vm:SelectableDataItemViewModel">
                <Grid ColumnDefinitions="Auto,2*,1.2*,1.2*,1*" Margin="0,3">
                  <CheckBox Grid.Column="0" Width="28"
                            IsChecked="{Binding IsSelected}"
                            VerticalAlignment="Center" />
                  <StackPanel Grid.Column="1" VerticalAlignment="Center">
                    <TextBlock Text="{Binding Name}" FontWeight="SemiBold" TextWrapping="Wrap" />
                    <TextBlock Text="{Binding Id}" Classes="subtle" FontSize="11" TextWrapping="Wrap" />
                  </StackPanel>
                  <TextBlock Grid.Column="2" Text="{Binding Type}" VerticalAlignment="Center" TextWrapping="Wrap" />
                  <TextBlock Grid.Column="3" Text="{Binding Category}" VerticalAlignment="Center" TextWrapping="Wrap" />
                  <TextBlock Grid.Column="4" Text="{Binding Units}" VerticalAlignment="Center" TextWrapping="Wrap" />
                </Grid>
              </DataTemplate>
            </ItemsControl.ItemTemplate>
          </ItemsControl>
        </ScrollViewer>

      </DockPanel>
    </Border>
  </DockPanel>
</UserControl>